Spectroscopic sensor and angle limiting filter

Abstract

An angle limiting filter includes: a first light-shielding layer containing a first light-shielding material and provided with a first opening; a second light-shielding layer containing a second light-shielding material and located in a region which surrounds at least one portion of the first light-shielding layer; a third light-shielding layer containing the first light-shielding material, provided with a second opening at least one portion of which overlaps the first opening, and located above the first light-shielding layer; and a fourth light-shielding layer containing the second light-shielding material and located above the second light-shielding layer in a region which surrounds at least one portion of the third light-shielding layer.

What is claimed is: 
     
       1. An angle limiting filter comprising:
 a first light-shielding layer containing a first light-shielding material and provided with a first opening; 
 a second light-shielding layer containing a second light-shielding material and located in a region which surrounds at least one portion of the first light-shielding layer; 
 a third light-shielding layer containing the first light-shielding material, the third light shielding layer being provided with a second opening at least one portion of which overlaps the first opening, the third shielding layer being located above the first light-shielding layer; and 
 a fourth light-shielding layer containing the second light-shielding material and located above the second light-shielding layer in a region which surrounds at least one portion of the third light-shielding layer. 
 
     
     
       2. The angle limiting filter according to  claim 1 , wherein
 the first light-shielding layer is in contact with an edge surface of the second light-shielding layer, and the third light-shielding layer is in contact with an edge surface of the fourth light-shielding layer. 
 
     
     
       3. The angle limiting filter according to  claim 1 , wherein
 the first light-shielding layer is provided with a plurality of the first openings, and includes a first portion located between two of the first openings next to each other and a second portion located closer to the side of the second light-shielding layer than the first portion and the plurality of first openings, and 
 the edge surface of the second light-shielding layer is located at the center of the width of the second portion of the first light-shielding layer, and covered with the first light-shielding layer. 
 
     
     
       4. The angle limiting filter according to  claim 1 , wherein
 a gap is disposed between the first light-shielding layer and the third light-shielding layer, and both the first light-shielding layer and the third light-shielding layer are in contact with a portion of the fourth light-shielding layer. 
 
     
     
       5. The angle limiting filter according to  claim 1 , wherein
 the reflectance of the first light-shielding material is lower than that of the second light-shielding material. 
 
     
     
       6. The angle limiting filter according to claim wherein
 the first and third light-shielding layers are configured with a material whose reflectance is lower than that of aluminum. 
 
     
     
       7. A spectroscopic sensor comprising:
 the angle limiting filter according to  claim 1 ; 
 a wavelength limiting filter which limits the wavelength of light capable of passing through the angle limiting filter; and 
 a light receiving element which detects light passed through the angle limiting filter and the wavelength limiting filter.